1. Field of the Invention
The present invention relates to an ink jet printhead, and, more particularly, to an ink jet printhead having a bubble chamber, and configured to minimize ink-flow dead zones in the bubble chamber.
2. Description of the Related Art
An imaging apparatus, such as an ink jet printer, forms an image on a print medium, such as paper, by applying ink to the print medium. Such an ink jet printer includes a reciprocating printhead carrier that transports one or more ink jet printheads across the print medium along a bi-directional scanning path defining a print zone of the printer. One such ink jet printer mounts a plurality of ink supply tanks, with each ink tank containing a supply of a particular color of ink, e.g., black, cyan, magenta, and yellow, and with each ink tank being in fluid communication with a respective ink jet printhead.
In one example, an ink jet printhead may be permanently attached to an ink supply tank to form an ink jet printhead cartridge, which is installed on the printhead carrier as an integral unit. In another example, an ink jet printhead assembly having an ink jet printhead is removably mounted to the printhead carrier, and an ink supply tank is removably mounted to the ink jet printhead assembly.
An ink jet printhead includes a substrate to which a nozzle plate is attached. Formed in the substrate is a bubble chamber. An actuator element is positioned, or formed, in the bubble chamber. The actuator element may be, for example, a resistive heater element or a piezoelectric element. An ink jet printhead that uses resistive heater elements also may be referred to as a thermal ink jet printhead. Heat generated by a heater element causes a vapor bubble to form in the bubble chamber, thus ejecting an ink droplet from a corresponding ink jet nozzle.
Referring to FIGS. 1A and 1B, there is shown a portion of a prior art ink jet printhead 10 configured with a bubble chamber 12 having two side ink inlets 14-1, 14-2 positioned along a lengthwise wall 12-1 of bubble chamber 12, and having a nozzle plate 16 having an ink jet nozzle 18 positioned over the center of bubble chamber 12. A resistive heater element 20 is suspended in bubble chamber 12. In this configuration, however, ink-flow dead zones tend to form in bubble chamber 12 due to the proximity of the ink inlets 14-1, 14-2 and ink jet nozzle 18. Deleteriously, air bubbles tend to accumulate in ink-flow dead-zones in bubble chamber 12 and their presence degrades the efficiency and regularity of energy transfer from the vapor bubble to the ink. The presence of air bubbles can reduce the velocity of an ink droplet ejected through the corresponding ink jet nozzle 18 of nozzle plate 16 and increase the variation among droplet ejections.
What is needed in the art is an ink jet printhead that is configured to minimize, i.e., reduce or eliminate, ink-flow dead zones in the bubble chamber.